Simulation of Nanofluid Heat Transfer Enhancement With LBM

2012 ◽  
Author(s):  
Yali Guo ◽  
Daoyang Qin ◽  
Shengqiang Shen ◽  
Hehan Xu ◽  
Yong Yang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Temperature Field ◽  
Buoyancy Force ◽  
Gravitational Force ◽  
Pure Liquid ◽  
Two Dimensional ◽  
Transfer Enhancement ◽  
Internal Forces ◽  
Simulation Results ◽  
Multi Phase

Heat transfer and fluid flow in a two-dimensional enclosure filled with nanofluids is investigated using multi-phase LBM, where the influences of external and internal forces, for example, the Bromnian force, gravitational force, drag force, buoyancy force and the interactions among particles on the molecular levels, are considered. The velocity field and the temperature field are obtained at different nanoparticles volume fractions, different buoyancy parameters. The simulation results show that nanofluids could enhance the heat transfer compared to pure liquid.

Characteristics of Heat Transfer and Flow on a Surface With Small-Scale Concave Spherical Pits

2008 ◽  
Author(s):  
J. S. Wang ◽  
Y. Qiu ◽  
L. Y. Li
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Small Scale ◽  
Heat Transfer Mechanism ◽  
Transfer Enhancement ◽  
Special Effect ◽  
Turbulent Drag Reduction ◽  
Turbulent Drag ◽  
Simulation Results ◽  
Turbulent Coherent Structure

Small-scale concave spherical pits, which have a special effect on heat transfer enhancement and turbulent drag reduction, are investigated by numerical simulation in detail. Two kinds of small-scale concave pits structures are designed on surface of a plate, which are located in the bottom of a rectangle channel. The characteristics of heat transfer and flow in channel are investigated and compared with a same channel with plate bottom by means of LES. Flow structure and temperature distribution near the pits are analyzed. The numerical simulation results indicate that the concave spherical pits disturb the flow field and vortex is induced by the pits. The turbulent coherent structure is affected by the induced vortex. The numerical simulation indicates that small scale pit can generate the vortex in couple. The range of vortex is accord with the array of small scale pit. The small scale pit can enhance the intensity of vortex. As a result, the temperature field near the pit is changed with generation of the vortex. The heat transfer mechanism on plate with small scale concave spherical pit is summarized.

Numerical Investigation of Heat Transfer in the Wake of a Single Highly Confined Bubble in a Horizontal Minichannel

2018 ◽  
Author(s):  
John R. Willard ◽  
D. Keith Hollingsworth
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Numerical Investigation ◽  
Channel Flow ◽  
Heat Generation ◽  
Reduced Order Model ◽  
Two Dimensional ◽  
Transfer Enhancement ◽  
Order Model ◽  
Reduced Order

Confined bubbly flows in millimeter-scale channels produce significant heat transfer enhancement when compared to single-phase flows. Experimental studies support the hypothesis that the enhancement is driven by a convective phenomenon in the liquid phase as opposed to sourcing from microlayer evaporation or active nucleation. A numerical investigation of flow structure and heat transfer produced by a single bubble moving through a millimeter-scale channel was performed in order to document the details of this convective mechanism. The simulation includes thermal boundary conditions emulating those of the experiments, and phase change was omitted in order to focus only on the convective mechanism. The channel is horizontal with a uniform-heat-generation upper wall and an adiabatic lower surface. A Lagrangian framework was adopted such that the computational domain surrounds the bubble and moves at the nominal bubble speed. The liquid around the bubble moves as a low-Reynolds-number unsteady laminar flow. The volume-of-fluid method was used to track the liquid/gas interface. This paper reviews the central results of this simulation regarding wake heat transfer. It then compares the findings regarding Nusselt number enhancement to a reduced-order model on a two-dimensional domain in the wake of the bubble. The model solves the advective-diffusion equation assuming a velocity field consistent with fully developed channel flow in the absence of the bubble. The response of the uniform-heat-generation upper wall is included. The model assumes a temperature profile directly behind the bubble which represents a well-mixed region produced by the passage of the bubble. The significant wake heat transfer enhancement and its decay with distance from the bubble documented by the simulation were captured by the reduced-order model. However, the channel surface temperature recovered in a much shorter distance in the simulation compared to the reduced-order model. This difference is attributed to the omission of transverse conduction within the heated surface in the two-dimensional model. Beyond approximately one bubble diameter into the bubble wake, the complex flow structures are replaced by the momentum field of the precursor channel flow. However, the properties and thickness of the heated upper channel wall govern the heat transfer for many bubble diameters behind the bubble.

Numerical Analysis of Heat Transfer Enhancement in a Micro-Channel Due to Mechanical Stirrers

2020 ◽  
Vol 13 (1) ◽  
Author(s):  
M. Sreejith ◽  
S. Chetan ◽  
S. N. Khaderi
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Enhancement ◽  
Peclet Number ◽  
Periodic Case ◽  
Two Dimensional ◽  
Transfer Enhancement ◽  
Fluidic Channel ◽  
Enhancement Of Heat Transfer ◽  
Péclet Number

Abstract Using two-dimensional numerical simulations of the momentum, mass, and energy conservation equations, we investigate the enhancement of heat transfer in a rectangular micro-fluidic channel. The fluid inside the channel is assumed to be stationary initially and actuated by the motion imparted by mechanical stirrers, which are attached to the bottom of the channel. Based on the direction of the oscillation of the stirrers, the boundary conditions can be classified as either no-slip (when the oscillation is perpendicular to the length of the channel) or periodic (when the oscillation is along the length of the channel). The heat transfer enhancement due to the motion of the stirrers (with respect to the stationary stirrer situation) is analyzed in terms of the Reynolds number (ranging from 0.7 to 1000) and the Peclet number (ranging from 10 to 100). We find that the heat transfer first increases and then decreases with an increase in the Reynolds number for any given Peclet number. The heat transferred is maximum at a Reynolds number of 20 for the no-slip case and at a Reynolds number of 40 for the periodic case. For a given Peclet and Reynolds number, the heat flux for the periodic case is always larger than the no-slip case. We explain the reason for these trends using time-averaged flow velocity profiles induced by the oscillation of the mechanical stirrers.

Heat transfer in a periodic boundary layer near a two-dimensional stagnation point

1972 ◽  
Vol 56 (4) ◽  
pp. 619-627 ◽  
Author(s):  
Hiroshi Ishigaki
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Temperature Field ◽  
Velocity Field ◽  
Stagnation Point ◽  
High Frequency ◽  
High Frequency Oscillation ◽  
Main Stream ◽  
Two Dimensional ◽  
Mean Temperature

Following the previous velocity-field study (Ishigaki 1970), this paper studies how the temperature field in the laminar boundary layer near a two-dimensional stagnation point responds to the main-stream oscillation. The time-mean temperature field is of particular interest and is studied in detail. The velocity field is treated as known and is taken from the previous paper. In § 3 the solutions over the whole frequency range are obtained under the assumption of small amplitude oscillation and the results are compared with the existing approximate solutions for low and high frequency in terms of heat transfer. Time-mean heat transfer decreases at low frequency, but slightly increases at high frequency. Two factors that cause time-mean modification of the temperature field are examined quantitatively. In § 4 the finite amplitude case is treated under the assumption of high-frequency oscillation and a few examples of the time-mean temperature profile are shown.

scholarly journals Effect of Squealer Tip on Rotor Heat Transfer and Efficiency

1997 ◽  
Author(s):  
A. A. Ameri ◽  
E. Steinthorsson ◽  
David L. Rigby
Keyword(s):  
Heat Transfer ◽  
Transfer Rate ◽  
Flow Structures ◽  
Two Dimensional ◽  
Transfer Enhancement ◽  
Flow And Heat Transfer ◽  
Significant Difference ◽  
Blade Tip ◽  
Large Heat ◽  
Good Agreement

Calculations were performed to simulate the tip flow and heat transfer on the GE-E3 first stage turbine, which represents a modern gas turbine blade geometry. Cases considered were a smooth tip, 2% recess, and 3% recess. In addition a two-dimensional cavity problem was calculated. Good agreement with experimental results was obtained for the cavity calculations, demonstrating that the k-ω turbulence model used is capable of representing flows of the present type. In the rotor calculations, two dominant flow structures were shown to exist within the recess. Also areas of large heat transfer rate were identified on the blade tip and the mechanisms of heat transfer enhancement were discussed. No significant difference in adiabatic efficiency was observed for the three tip treatments investigated.

Free Convection in an Open Triangular Cavity Filled With a Nanofluid Under the Effects of Brownian Diffusion, Thermophoresis and Local Heater

2017 ◽  
Vol 140 (4) ◽  
Author(s):  
Nadezhda S. Bondareva ◽  
Mikhail A. Sheremet ◽  
Hakan F. Oztop ◽  
Nidal Abu-Hamdeh
Keyword(s):  
Heat Transfer ◽  
Buoyancy Force ◽  
Local Heat ◽  
Brownian Diffusion ◽  
Governing Equations ◽  
Transfer Enhancement ◽  
Two Phase ◽  
Force Magnitude ◽  
Flow And Heat Transfer ◽  
Buoyancy Ratio

Natural convection of a water-based nanofluid in a partially open triangular cavity with a local heat source of constant temperature under the effect of Brownian diffusion and thermophoresis has been analyzed numerically. Governing equations formulated in dimensionless stream function and vorticity variables on the basis of two-phase nanofluid model with corresponding initial and boundary conditions have been solved by finite difference method. Detailed study of the effect of Rayleigh number, buoyancy-ratio parameter, and local heater location on fluid flow and heat transfer has been carried out. It has been revealed that an increase in the buoyancy force magnitude leads to homogenization of nanoparticles distribution inside the cavity. A growth of a distance between the heater and the cavity corner illustrates the heat transfer enhancement.

scholarly journals A Numerical Research of Heat Transfer in Rectangular Fins with Different Perforations

2019 ◽  
Vol 8 (12S) ◽  
pp. 367-371
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Buoyancy Force ◽  
Temperature Drop ◽  
Density Variation ◽  
Transfer Enhancement ◽  
Enhancement Of Heat Transfer ◽  
Numerical Research

Heat Transfer enhancement needs buoyancy force. This is to be achieved by making perforations on fin surfaces. The present paper is a study on the enhancement of heat transfer in terms of density, velocity and temperature with three different perforation geometry (parallel square, inclined square and circular). CFD was used to carry out the study of density variation, velocity and temperature drop among different perforated fins. This type of perforated fin has an improvement in heat transfer rate over its dimensionally equivalent solid fin.

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